Objectives:
Mupirocin is a topical antibiotic commonly used for treament of
S. aureus and streptococcal skin and soft tissue infections (SSTI) as well as for nasal decolonization of methicillin-resistant
S. aureus (MRSA) in preoperative carriers. High-level mupirocin resistance (HLR) is associated with decolonization failure. We aimed to evaluate mupirocin HLR rates in MRSA SSTI isolates from 24 clinical laboratories.
Results:
MRSA isolates from 401 SSTI cases were screened by PCR for the presence of the plasmid-encoded
mupA (
ileS-2) gene that confers high-level mupirocin resistance. The gene was found in 85 (21.2%) of the strains and was more prevalent in PVL-positive MRSA (28.4% of 109 strains) compared with PVL-negative MRSA (18.5% of 292 strains). The
qacA/B gene that is associated with chlorhexidine MIC elevation was found in 35 (41%) of the
mupA-positive strains.
Phenotypic HLR was confirmed in 85% of the mupA PCR-positive strains. Multidrug resistance (≥3 non-b-lactam antibiotics) was observed in 54% of mupA-positive strains and in 71% of strains positive both for mupA and qacA/B. The antibiotic resistance profile of the mupirocin resistant strains was ciprofloxacin (95%), erythromycin (84%), clindamycin (54%), gentamicin (38%) and trimethoprim/sulfamethoxazole (4%).
Mupirocin resistant strains contained 18 different spa types, predominantly t008 (34%) and t002 (24%). The PVL-positive, mupirocin-resistant strains were primarily of the USA300 type, while PVL-negative strains were diverse by PFGE analysis.
Conclusion:
Genotypic and phenotypic mupirocin HLR were observed respectively in 21% and 18% of MRSA isolates from SSTI.
High prevalence of HLR warrants susceptibility testing and prudent mupirocin use.
